Feed and transfer systems for presses are well known. Generally the systems have had movements in three directions and six senses of directions upon each cycle or each stepping of an article to a next adjacent press station. An inward movement gripped the piece, an upward movement lifted the piece, a forward movement carried the piece to the next station. A downward movement deposited the article or workpiece at the next die station, an outward movement released the piece and a rearward movement returned the transfer to its original position for beginning the next forward stepping cycle.
Use of underdrive presses has reduced the necessary transfer steps. Upper dies are held stationary and lower dies move up to force and shape the articles against the upper dies. Since the upward movement of the lower dies may lift and remove the articles from the transfer, the transfer apparatus can avoid the lifting and lowering and gripping and releasing steps. Thus transfer movement can be limited to one direction and two senses of direction or simply pure forward and rearward reciprocation.
As a result press operations may be speeded and complexities of mechanical movements may be reduced. To increase reliability of the high speed systems, it is necessary that the transfer drive be accurate and capable of resisting torques and capable of many cycles of operation without losing accuracy. It is necessary that articles be fed into the transfer apparatus repeatedly at high rates of speed without jamming and it is necessary that the transfer have provisions for gripping the article securely against floating and turning without scoring or scratching or otherwise damaging parts of articles which are gripped. It is necessary to support the transfer bars with accuracy and at the same time the least resistance to sliding and cam loading as is possible.
Examples of prior art attempts and finding solutions to the on-going problems are found in patents collected in International Class B21D 43 and 51 and U.S. Class 113, subclasses 113 and 114.